As is well known, liquid crystal displays (LCDs) are widely used as flat panel displays such as TVs, computer monitors, or the like. A back light unit (BLU) is a luminary part which emits light behind the LCD. Meanwhile, the BLU includes a light guide panel which guides the light incident from a side surface to a front surface. Recently, light emitting diode (LED) arrays have been used as side surface line light sources of light guide panels.
FIGS. 1A and 1B are a front view and a plan view of a conventional LED array, respectively. As shown in FIGS. 1A and 1B, in the LED array used as a conventional side surface line light source for a BLU, a plurality of LED chips 20 are disposed on a printed circuit board 10 at intervals. In each LED chip 20 of the above-described configuration, an LED chip 20 is bonded through wire bonding 28 on an upper surface of an aluminum substrate 22 (hereinafter referred to as “a chip substrate”) with vertical insulating layer 24 interposed therebetween to provide mutual insulation. The LED chip 20 is mounted inside a cavity having a groove formed a predetermined depth from the upper surface of the chip substrate 22 in order to improve reflection performance. In this case, the chip substrate 22 insulated by the vertical insulating layer 24 may serve as a (+) or (−) electrode terminal.
Hereinafter, various devices including the LED, which emits light, are generically referred to as “an optical device,” and a product in which two or more optical devices are arranged side-by-side in a matrix form is called “an optical device array.”
However, according to the conventional optical device array described above, since the optical device chip is mounted on the printed circuit board in a supine state, the light is emitted from the optical device chip in an upward direction (based on FIG. 1A). Thus, as an overall thickness of corresponding back light (as a result, a flat panel display) depends on a width of the printed circuit board, there has been a problem reduction in a thickness of the flat panel display is limited.